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A078998
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Choose a(n) so that a(1)+a(2)+...+a(n) = concatenation of n first natural numbers.
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0
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1, 11, 111, 1111, 11111, 111111, 1111111, 11111111, 111111111, 12222222121, 1222222212101, 122222221210101, 12222222121010101, 1222222212101010101, 122222221210101010101, 12222222121010101010101
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OFFSET
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1,2
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LINKS
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Table of n, a(n) for n=1..16.
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FORMULA
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a(1)=1; for n>1, a(n) = A007908(n)-A007908(n-1)
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MATHEMATICA
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b = {}; a = {}; Do[w = RealDigits[n]; w = First[w]; Do[AppendTo[a, w[[k]]], {k, 1, Length[w]}]; p = FromDigits[a]; AppendTo[b, p], {n, 1, 30}]; c = {}; Do[AppendTo[c, b[[n + 1]] - b[[n]]], {n, 1, Length[b] - 1}]; c (* Artur Jasinski, Mar 30 2008 *)
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CROSSREFS
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Cf. A000422, A116504, A007908, A116505, A104759, A138789, A138790, A138793.
Sequence in context: A000042 A002275 A294348 * A078191 A097115 A134732
Adjacent sequences: A078995 A078996 A078997 * A078999 A079000 A079001
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KEYWORD
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nonn,base
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AUTHOR
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Benoit Cloitre, Jan 12 2003
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STATUS
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approved
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